1. Field of the Invention
The present invention relates generally to so-called F-connectors used primarily in the cable television industry to connect coaxial cables to threaded ports, and more particularly to such F-connectors that are installed using an axial compression tool.
2. Description of the Related Art
Coaxial cable F-connectors are often used to terminate a drop cable in a cable television system. The coaxial cable typically includes a center conductor surrounded by a dielectric, in turn surrounded by a conductive grounding foil and/or braid (hereinafter referred to as a conductive grounding sheath); the conductive grounding sheath is itself surrounded by a protective outer jacket. The F-connector is secured over the prepared end of the jacketed coaxial cable, allowing the end of the coaxial cable to be threadedly connected with a threaded port of a terminal block.
Crimp style F-connectors are known wherein a crimp sleeve is included as part of the connector body. A special radial crimping tool, having jaws that form a hexagon, is used to radially crimp the crimp sleeve around the outer jacket of the coaxial cable to secure such a crimp style F-connector over the prepared end of the coaxial cable. Examples of such crimp connectors are disclosed within U.S. Pat. No. 4,400,050 to Hayward, assigned to Gilbert Engineering Co., Inc.; and U.S. Pat. No. 4,990,106 to Szegda, assigned to John Mezzalingua Assoc. Inc.
It is known in the art that the passage of moisture between the coaxial cable jacket and the surrounding F-connector can lead to corrosion, increased contact resistance, reduced signal strength, and excessive RF leakage from the connector. Those skilled in the art have made various efforts to form a seal between the F-connector and the jacket of the coaxial cable to preclude such moisture ingress. F-connectors are known in the cable television industry wherein special sealing compounds are included in an effort to form leakproof seals. For example, U.S. Pat. No. 4,755,152 to Elliot, et al., and assigned to Tele-Communications, Inc. discloses a crimp connector incorporating a glob of a gel or other movable sealing material within a cavity of the connector to form a seal between the jacket of the coaxial cable and the interior of the F-connector.
Still another form of F-connector is known wherein an annular compression sleeve is used to secure the F-connector over the prepared end of the cable. Rather than crimping a crimp sleeve radially toward the jacket of the coaxial cable, these F-connectors employ a plastic annular compression sleeve that is initially attached to the F-connector, but which is detached therefrom prior to installation of the F-connector. The compression sleeve includes an inner bore for following such compression sleeve to be passed over the end of the coaxial cable prior to installation of the F-connector. The F-connector itself is then inserted over the prepared end of the coaxial cable. Next, the compression sleeve is compressed axially along the longitudinal axis of the connector into the body of the connector, simultaneously compressing the jacket of the coaxial cable between the compression sleeve and the tubular post of the connector. An example of such a compression sleeve F-connector is shown in U.S. Pat. No. 4,834,675 to Samchisen and assigned to LRC Electronics, Inc.; such patent discloses a compression sleeve type F-connector known in the industry as "Snap-n-Seal". A number of commercial tool manufacturers provide compression tools for axially compressing the compression sleeve into such connectors; for example, the CablePrep division of Ben Hughes Communication Products Company of Chester, Conn. sells such a hand-operated compression tool under the commercial designation "Terminx".
The aforementioned "Snap-n-Seal" compression connector requires substantial manipulation by an installer. The installer must detach the annular compression sleeve from the connector, slide the compression sleeve over the end of the coaxial cable, then install the connector, and finally compress the compression sleeve into the body of the connector. During assembly, the compression sleeve can easily become lost. In addition, such "Snap-n-Seal" connectors are significantly more expensive than conventional crimp style connectors.
A somewhat related radial compression-type F-connector is disclosed within U.S. Pat. No. 5,470,257 to Szegda. A tubular locking member protrudes axially into the open rear end of the outer collar or sleeve. The tubular locking member is displaceable axially within the outer collar between an open position accommodating insertion of the tubular post into the prepared end of the coaxial cable, and a clamped position fixing the end of the cable within the F-connector. An O-ring is mounted on the rear end of the tubular locking member to seal the connection between the tubular locking member and the outer collar as the tubular locking member is axially compressed. Such connectors have been sold in the past under the designation "CMP". The O-ring provided on the tubular locking member is exposed and unprotected prior to axial compression of the F-connector.
It is known in the coaxial cable field generally that collars or sleeves within a coaxial cable connector can be compressed inwardly against the outer surface of a coaxial cable to secure a coaxial cable connector thereto. For example, in U.S. Pat. No. 4,575,274 to Hayward and assigned to Gilbert Engineering Company Inc., a connector assembly for a signal transmission system is disclosed wherein a body portion threadedly engages a nut portion. The nut portion includes an internal bore in which a ferrule is disposed, the ferrule having an internal bore through which the outer conductor of a coaxial cable is passed. As the nut portion is threaded over the body portion, the ferrule is wedged inwardly to constrict the inner diameter of the ferrule, thereby tightening the ferrule about the outer surface of the cable. However, the connector shown in the Hayward '274 patent is much more expensive than conventional F-connectors and can not be installed quickly, as by a simple crimp or compression tool; rather, the mating threads of such connector must be tightened, as by using a pair of wrenches.
Accordingly, it is an object of the present invention to provide a simple and inexpensive F-connector that can easily be machined from a small number of components, and which can be quickly installed over the prepared end of a coaxial cable using a conventional F-connector axial compression installation tool.
It is another object of the present invention to provide such an F-connector that does not require any threaded, rotational movement of the connector components during installation in order to secure such connector over the end of the coaxial cable.
It is still another object of the present invention to provide such an F-connector which forms a reliable moisture proof sea l between the F-connector and the jacket of the coaxial cable to preclude moisture from passing between the F-connector and the jacket of the coaxial cable extending therein, while avoiding the need for gels or other sealing compounds.
A further object of the present invention to provide such an F-connector that is shipped to a user as a one-piece structure, and which is installed onto the end of a coaxial cable as a one piece structure without detachment of any components, in order to simplify the installation of such connector over the end of a coaxial cable, and to avoid the loss of detachable components.
Still another object of the present invention is to provide such an F-connector which avoids the need for the assembly of any O-rings for the purpose of creating a seal between the connector and the jacket of the cable.
A further object of the present invention is to increase the pull-out strength of the F-connector/coaxial cable assembly by making it more difficult to dislodge the cable jacket from the F-connector following installation.
These and other objects of the present invention will become more apparent to those skilled in the art as the description of the present invention proceeds.